COMPLEMENTAL MALE. 273 



(PL VI, figs. 6 and 3), we must be struck with the diffe- 

 rences in their shape, in the number, relative sizes, and 

 forms of the several valves. It should, however, be borne 

 in mind, that the scuta and carina in the hermaphrodite 

 at first grow exclusively downwards ; so that if we remove 

 the upper portions subsequently added, the difference in 

 shape in these valves is not so great as it at first appears. 

 The rostrum in the male is of much larger relative size ; 

 whilst of the upper latera there is not a trace, although 

 in the hermaphrodite these valves are larger than the 

 rostrum. The terga, compared with those of the herma- 

 phrodite, differ more essentially than do the other valves ; 

 and the manner in which the primordial valves project, 

 shows that from the first commencement of calcification, 

 the lines of growth have followed an unusual course. The 

 great breadth and shortness of the terga is evidently re- 

 lated to the shortening of the whole capitulum, and the 

 transverse position of the orifice ; and this shortening of 

 the capitulum, no doubt, is rendered necessary for its 

 reception and protection within the shallow furrow be- 

 tween the scuta of the hermaphrodite. Finally, if we 

 compare the internal parts of the hermaphrodite and 

 male, the differences are considerable, though partly 

 to be accounted for by the youth of the latter : the form 

 and position of the labrum, and the distance between the 

 first and second pair of cirri, is the same in both ; but 

 the mandibles and maxillae differ considerably. 



To put the case as I have before done, if a specimen 

 of one of these parasites had been brought to me to class 

 without any information of its habits, — the downward 

 direction of growth in all the valves, the presence of a 

 rostrum, the villose outer integument, all the details of 

 the prehensile antennae, the form of the animal's body, 

 and the position of the labrum, would have convinced me 

 that, though a quite new genus, it ought to have stood 

 close to Scalpellum, and nearer to it than to Ibla. 



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